1. Field of the Invention
The present invention relates to an input device, and particularly relates to an input device that allows electrical property inspection of a transparent electrode layer to be easily performed and that allows the uniformity of a capacitance distribution to be improved.
2. Description of the Related Art
At present, light-transmissive type input devices for performing a coordinate input when a menu item or an object in a display image is operated directly with a finger or the like are used as display units of portable electronic apparatuses and the like. There are some operation modes of such input devices. Among them, capacitance type input devices are widely used.
FIG. 11 shows an exploded perspective view of a capacitance type input device 101 disclosed in Japanese Unexamined Patent Application Publication No. 2010-277461. As shown in FIG. 11, the input device 101 of the related art example includes a scanning side board 130 and a detection side board 140. A plurality of scanning electrodes 131 extending in a Y1-Y2 direction are formed on the scanning side board 130, and a plurality of detection electrodes 141 extending in an X1-X2 direction are formed on the detection side board 140. Scanning side connection electrodes 133 for connecting to a flexible printed board (not shown) are formed at the ends of the scanning electrodes 131 on the Y2 side, respectively, and detection side connection electrodes 143 are similarly formed at the ends of the detection electrodes 141 on the X1 side.
The scanning side board 130 and the detection side board 140 are disposed so as to face each other such that capacitances are provided between the scanning electrodes 131 and the detection electrodes 141. When a finger or the like is caused to contact the surface of the input device 101, a capacitance value between the scanning electrode 131 and the detection electrode 141 at the touched position changes. On the basis of the change of the capacitance value, the input position can be detected. In the input device 101 of the related art, a shield layer 163 is formed so as to surround the detection electrodes 141, thereby preventing false detection or change in detection sensitivity that is caused by external noise.
However, the scanning electrodes 131 and the detection electrodes 141 are formed of a transparent electrode film of ITO (Indium Tin Oxide) or the like, and the scanning side connection electrodes 133 and the detection side connection electrodes 143 are formed of a low-resistance metal material such as copper and silver for ensuring connection reliability. Thus, near the ends of the scanning electrodes 131 on the Y2 side to which the scanning side connection electrodes 133 are connected, a capacitance value between the scanning side board 130 and the detection side board 140 changes due to the difference between the dielectric constants and influence of the thicknesses of the materials.
In other words, different capacitance distributions are formed at both ends of the scanning electrodes 131 in the Yl-Y2 direction. Thus, the capacitance values in an input region of the input device 101 become ununiform, and decrease in detection sensitivity, false detection, or the like may occur.
Further, when electrical property inspection of the scanning electrodes 131 is performed on the scanning side board 130, it is necessary to cause a probe pin for inspection to contact each scanning electrode 131, since the scanning side connection electrode 133 is formed at one end of each scanning electrode 131 but no electrode is formed at the other end of each scanning electrode 131. However, the transparent electrode film is in general a material in which a crack is likely to occur. Thus, when the probe pin is caused to directly contact each scanning electrode 131 to perform measurement, the electrical properties and the environmental resistance of each scanning electrode 131 may deteriorate. Thus, it is difficult to perform the inspection at an early stage prior to assembling the input device 101, and the inspection is performed after assembling the input device 101. As a result, finding a defect is delayed, and the manufacturing cost increases.